This invention relates generally to an arrangement for sealing a lead from a confined cavity of an apparatus and more particularly to an externally mounted mechanical sealing arrangement.
Various attempts have been set forth to seal lead wires or pins extending from a coil that is encapsulated within a plastic overmold. In some of these attempts, a cavity is formed within the overmold and the lead wires or pins from the coil extend into the cavity and a rubber grommet is disposed within the cavity. The lead wires extend through holes within the grommet and are sealed by a compressive force exerted on the outer circumference of the grommet. Many times, in these attempts, it is difficult to mold the plastic material around the leads extending therethrough.
Many other arrangements are known for connecting leads to coils having overmold disposed around the coil. In these other arrangements, the leads that extend from the coil through the overmold may not be totally sealed from the outside atmosphere when being subjected to varying temperature. It is well known that when a coil is produced that small voids are present after the winding is placed on the bobbin and the plastic overmold material is injected around the coil. During an increase in temperature, the pressure of the air within these voids expands thus producing an increase in pressure therein which, if not properly sealed, escapes around the leads that pass through the overmold. Likewise, as the temperature decreases, a pressure less than atmospheric is created within the voids. Consequently, if the leads are not properly sealed, air is drawn into the voids from the outside atmosphere. If the coil is being used in an environment containing contaminants, the contaminants are drawn into the voids and cause premature failure of the coil. Therefore, it is desirable to provide a positive seal so that contaminants cannot be drawn into the coil or sealed cavity. Likewise, it is desirable to provide such a seal arrangement to seal around other types of leads to protect sensitive components disposed in an otherwise sealed cavity from outside contaminants.
One solution to these problems and complications is disclosed in Palmer et al., U.S. Pat. No. 6,175,083, the entire disclosure of which is hereby incorporated by reference. As set forth therein, a disc shaped grommet member is retained in sealing relationship with lead wires by the combination of a separate cap member and a separate collar. The collar is integrally melted and molded to both the mounting portion of the coil overmold and to the cap member. By integrally melting and molding the collar over the cap and mounting portion of the overmold, there is no possibility for water to enter the enclosed cavity between the cap and the mounting portion. This design has met the standards of different Original Equipment Manufacturers (OEMs which require a dunk test in a water solution comprised of water, detergent and/or salt (each OEM uses different times, temperatures and depths for the dunk test) to ensure that no water reaches the wire coil cavity (e.g. the wire coil cavity is hermetically sealed).
While the design of ""083 patent has provided a solution and has met with substantial commercial success, it does require a second molding operation to integrally mold and melt the collar over the cap member and mounting portion of the coil overmold. This is undesirable as it has required further cost and labor associated with this second molding operation.
In light of the above, and according to one aspect of the present invention, it is an objective of the present invention to provide a seal mechanism design for an electrical lead extending from a closed cavity (e.g. an overmold of a wire coil) that utilizes a less expensive method and apparatus to adequately seal the closed cavity from water and/or other contaminants in the external environment.
According to an aspect of the present invention, it is an objective of the present invention to eliminate a second molding operation in the assembly of solenoid assemblies such as those set forth in the background section above.
In that regard, it is a further object of the present invention to provide a less expensive way to provide a solenoid assembly that successfully passes dunk tests as described in the background section above.
According to another aspect of the present invention, it is another objective of the present invention to provide a more effective sealing grommet design for sealing an electrical lead extending from a closed cavity (e.g. an overmold of a wire coil).
In accordance with these and other aims and objectives, the present invention is directed at a new sealing mechanism comprising a cap and a grommet for an electrical lead extending from a coil overmold or closed cavity. The grommet provides a first seal against the electrical lead and a second seal against a mounting section around the electrical lead. The cap is retained on the mounting portion for the lead through engagement between corresponding retaining structures on the cap and the mounting portion.
According to one aspect of the present invention, the grommet comprising a skirt section and a cover section. The skirt section forms a radial seal against the mounting portion while the cover section seals against the electrical leads.
According to another aspect of the present invention, the cap mechanically snaps onto the mounting portion. The cap serves to secure the grommet to the mounting portion.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.